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1//===-- nextafter implementation for x86 long double numbers ----*- C++ -*-===//2//3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.4// See https://llvm.org/LICENSE.txt for license information.5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception6//7//===----------------------------------------------------------------------===//8 9#ifndef LLVM_LIBC_SRC___SUPPORT_FPUTIL_X86_64_NEXTAFTERLONGDOUBLE_H10#define LLVM_LIBC_SRC___SUPPORT_FPUTIL_X86_64_NEXTAFTERLONGDOUBLE_H11 12#include "src/__support/macros/config.h"13#include "src/__support/macros/properties/architectures.h"14 15#if !defined(LIBC_TARGET_ARCH_IS_X86)16#error "Invalid include"17#endif18 19#include "hdr/stdint_proxy.h"20#include "src/__support/CPP/bit.h"21#include "src/__support/FPUtil/FEnvImpl.h"22#include "src/__support/FPUtil/FPBits.h"23 24namespace LIBC_NAMESPACE_DECL {25namespace fputil {26 27LIBC_INLINE long double nextafter(long double from, long double to) {28 using FPBits = FPBits<long double>;29 FPBits from_bits(from);30 if (from_bits.is_nan())31 return from;32 33 FPBits to_bits(to);34 if (to_bits.is_nan())35 return to;36 37 if (from == to)38 return to;39 40 // Convert pseudo subnormal number to normal number.41 if (from_bits.get_implicit_bit() == 1 && from_bits.is_subnormal()) {42 from_bits.set_biased_exponent(1);43 }44 45 using StorageType = FPBits::StorageType;46 47 constexpr StorageType FRACTION_MASK = FPBits::FRACTION_MASK;48 // StorageType int_val = from_bits.uintval();49 if (from == 0.0l) { // +0.0 / -0.050 from_bits = FPBits::min_subnormal(from > to ? Sign::NEG : Sign::POS);51 } else if (from < 0.0l) {52 if (to < from) { // toward -inf53 if (from_bits == FPBits::max_subnormal(Sign::NEG)) {54 // We deal with normal/subnormal boundary separately to avoid55 // dealing with the implicit bit.56 from_bits = FPBits::min_normal(Sign::NEG);57 } else if (from_bits.get_mantissa() == FRACTION_MASK) {58 from_bits.set_mantissa(0);59 // Incrementing exponent might overflow the value to infinity,60 // which is what is expected. Since NaNs are handling separately,61 // it will never overflow "beyond" infinity.62 from_bits.set_biased_exponent(from_bits.get_biased_exponent() + 1);63 if (from_bits.is_inf())64 raise_except_if_required(FE_OVERFLOW | FE_INEXACT);65 return from_bits.get_val();66 } else {67 from_bits = FPBits(StorageType(from_bits.uintval() + 1));68 }69 } else { // toward +inf70 if (from_bits == FPBits::min_normal(Sign::NEG)) {71 // We deal with normal/subnormal boundary separately to avoid72 // dealing with the implicit bit.73 from_bits = FPBits::max_subnormal(Sign::NEG);74 } else if (from_bits.get_mantissa() == 0) {75 from_bits.set_mantissa(FRACTION_MASK);76 // from == 0 is handled separately so decrementing the exponent will not77 // lead to underflow.78 from_bits.set_biased_exponent(from_bits.get_biased_exponent() - 1);79 return from_bits.get_val();80 } else {81 from_bits = FPBits(StorageType(from_bits.uintval() - 1));82 }83 }84 } else {85 if (to < from) { // toward -inf86 if (from_bits == FPBits::min_normal(Sign::POS)) {87 from_bits = FPBits::max_subnormal(Sign::POS);88 } else if (from_bits.get_mantissa() == 0) {89 from_bits.set_mantissa(FRACTION_MASK);90 // from == 0 is handled separately so decrementing the exponent will not91 // lead to underflow.92 from_bits.set_biased_exponent(from_bits.get_biased_exponent() - 1);93 return from_bits.get_val();94 } else {95 from_bits = FPBits(StorageType(from_bits.uintval() - 1));96 }97 } else { // toward +inf98 if (from_bits == FPBits::max_subnormal(Sign::POS)) {99 from_bits = FPBits::min_normal(Sign::POS);100 } else if (from_bits.get_mantissa() == FRACTION_MASK) {101 from_bits.set_mantissa(0);102 // Incrementing exponent might overflow the value to infinity,103 // which is what is expected. Since NaNs are handling separately,104 // it will never overflow "beyond" infinity.105 from_bits.set_biased_exponent(from_bits.get_biased_exponent() + 1);106 if (from_bits.is_inf())107 raise_except_if_required(FE_OVERFLOW | FE_INEXACT);108 return from_bits.get_val();109 } else {110 from_bits = FPBits(StorageType(from_bits.uintval() + 1));111 }112 }113 }114 115 if (!from_bits.get_implicit_bit())116 raise_except_if_required(FE_UNDERFLOW | FE_INEXACT);117 118 return from_bits.get_val();119}120 121} // namespace fputil122} // namespace LIBC_NAMESPACE_DECL123 124#endif // LLVM_LIBC_SRC___SUPPORT_FPUTIL_X86_64_NEXTAFTERLONGDOUBLE_H125